Display full text of posts on front page?

Hope this isn’t too basic. I’d like to display the full text of posts on the front page (I don’t use a static front page, currently). But I can’t find a way to do that in regular options, which means it’s likely (based on experience with other themes in the past) that I’ll need to create a child theme and fiddle around with one or more of the php files. My question is: which one(s)? Can you point me to the specific line(s) of code that need to be altered to allow the front page to display full text of posts instead of excerpts? Thanks in advance.